用R中另一列中的值替换特定列中的非NA值

我试图将合并表数据框的City.x列中的值替换为City.y列中的值，只要City.y列中没有NA。

换句话说，我想替换City.x列中除NA之外的所有值。

这是我到目前为止的代码：

library(tidyverse)
library(dplyr)

# Import food data
food <-
  read_csv(file = 'https://s3.amazonaws.com/notredame.analytics.data/inspections.csv', 
           col_names=c("ID", 
                       "DBAName", 
                       "AKAName", 
                       "License", 
                       "FacilityType",
                       "Risk",
                       "Address",
                       "City",
                       "State",
                       "ZIP",
                       "InspectionDate",
                       "InspectionType",
                       "Results",
                       "Violations",
                       "Latitude",
                       "Longitude",
                       "Location"), 
           col_types = "icccffcfffcffcddc",
           skip = 1)

# Change InspectionDate from character type to datetime type
food$InspectionDate <- strptime(food$InspectionDate, "%m/%d/%Y")

#Import zipcode data
zipcode <- 
  read_csv('https://s3.amazonaws.com/notredame.analytics.data/zipcode.csv', 
           col_names = c("ZIP",
                         "City", 
                         "State",
                         "Latitude",
                         "Longitude"),
           skip = 1)

# Convert ZIP, City, and State from character type to factor type
zipcode$ZIP <- as.factor(zipcode$ZIP)
zipcode$City <- as.factor(zipcode$City)
zipcode$State <- as.factor(zipcode$State)

#Correct zip codes (told these were incorrect)
food <- food %>%
  mutate(food$ZIP = ifelse("60627", "60827", ZIP))

#Create merged table from food and zipcode tables
mergedtable <- merge(x=food,y=zipcode,by="ZIP",all.x=TRUE)

#new_DF <- mergedtable[is.na(mergedtable$ZIP),]

mergedtable <- mergedtable %>%
  mutate(mergedtable$City.x = ifelse(!is.na(mergedtable$City.y), mergedtable$City.y, mergedtable$City.x))

mergedtable$City.x <- ifelse(!is.na(mergedtable$City.y), mergedtable$City.y, mergedtable$City.x)

最后两行代码都没有执行我想要的操作。第一个返回错误：

Error: unexpected '=' in:  
"mergedtable <- mergedtable %>%  
  mutate(mergedtable$City.x ="

最后一行将mergedtable $ City.x中的值转换为数字，但我不确定数字来自何处。